By default, Lion hides the user library folders in the Finder. You can still open them by pressing Cmd-Shift-G and typing the folder name in manually, but if you access the folder often, this can prove tedious. Note that thus far, every update (10.7.1 and 10.7.2) has reset the folder flags to hidden, so a simple repeat of the command will make them reappear. Simply type the following into your favourite Terminal, and your user library will appear:chflags nohidden ~/Library
Also, should you want to make all user libraries visible, use the following:sudo chflags nohidden /Users/*/Library

Many tweaks exist through the Terminal command defaults. Some of those specific to Mac OS X 10.7 have been included in Lion Tweaks, a standalone app. Also, there is a wonderful prefpane called Secrets, but while many of the tweaks available there still work on Lion, it has not yet been updated with new "secrets", so listed below are some of the tweaks I've found:

Periodically you may try to install/download/update an app in the Mac App Store (MAS) and it will sit there "waiting" indefinitely. Restarting the MAS doesn't seem to help. What did work for me was the following:

Quit the Mac App Store.

Navigate to /Applications/Utilities/

Open Activity Monitor.app

Search for "storeagent".

Select it, choose "Quit Process".

When asked if you really want to quit the process, choose "Quit".

Open the MAS and try to download the app again.

Note: Before you do this, you can also try holding Option, and it will give you a chance to "Cancel" the download, but this didn't seem to fix the issue for me.